I have a single radiator (central heating type) of size 70cm*75cm, circa
1976, that I need to replace. It is in a small bathroom and was wondering
what wattage output it was likely to give. Does anyone know or know a
formula to calculate it?
In article , DUMBO
Courtesy of John Stumbles 17 Jan, 00:32
Subject: Radiator output formula and finless rad specs
After a bit of firkling around with Myson & Kudox radiator output specs
found a formula which gives a reasonable approximation so one can
calculate output from dimensions (and v.v.)
Heat Output = (Height + 12) * Length * FACTOR
(Watts) (cm) (cm)
where FACTOR is (for Delta-T 50°C) * 0.13 for SC
* 0.19 for DP
* 0.24 for DC
might be useful to be able to calculate the output of
radiators without convection fins. Anyone have any data sheets on these?
 or at least, marginally interesting :-)
In article ,
You need to watch out for the average temperature which is claimed
to generate the specified power, and then correct for real values
(or if comparing, ensure the two datasheets are using the same value
for average temperature). When I was designing my system, some of
the manufacturer data sheets had small print saying values were at
80C average temperature. Not even a conventional system is likely
to ever reach that, as that's typically the maximum flow temperature.
(They're usually given as the delta, i.e. difference between room
temperature and average radiator temperature, so a delta of 60C
would typically be a room temperature of 20C + 60C delta = 80C
average radiator temperature, which just isn't realistic.)
In an earlier contribution to this discussion,
Assuming it has no fins on the back, a reasonable rule of thumb would be
1280 watts /M^2 at a Delta-T of 60 degC.
For the size quoted, this would equate to about 670 watts.
If your system is running at a lower Delta-T than this, the output will need
to be downrated. For example, at a Delta-T of 50 degC it would be about 530